A film highlighting British arms sales to Saudi Arabia that are reportedly used in the conflict in Yemen has been released by the charity Save the Children in time for one of the world's largest arms fairs taking place in London on Tuesday.

The provocative film Made in Britain calls on the British government to suspend arms sales to states in the Saudi Arabia-led coalition fighting in Yemen.

The Defence and Security Equipment International (DSEI) exhibition, which runs from Tuesday, is held every two years in London.

"For me, as a proud Brit, this is completely unacceptable," said Dominic West, a British actor who has appeared in US thriller series The Wire and voices the short film.

"We are providing aid to Yemen, but also selling weapons which are being used in a country where children are being bombed and starved," West said in a statement.

The UK has approved £3.8bn ($5bn) of arms licences to Saudi Arabia since the conflict escalated in March 2015 with exports including Paveway IV missiles and Typhoon fighter jets, according to Save the Children.

A poll commissioned by the charity found that more than half of the British public thought Britain should suspend the approval of arms sales to countries fighting in Yemen.

"The UK government takes its defence export responsibilities very seriously and already operates one of the most robust export control regimes in the world," a British government spokesman told the Thomson Reuters Foundation.

The United Nations has verified 5,144 civilian deaths in the war in Yemen, mainly from air strikes by the Saudi-led coalition, and an international investigation is urgently needed, UN human rights chief Zeid Ra'ad al-Hussein said on Monday.

The UN says the civil war has created the world's biggest humanitarian crisis, with the conflict sparking an economic collapse that has pushed millions to the brink of famine.

The film closes with the phrase: "Our greatest export should be hope, not fear."